Optical Components

Abstract

As the THz region is between the IR and mmW parts of the electromagnetic spectrum the types of components are, on the one hand, similar to optical equipment, for example mirrors and lenses, while, on the other hand, mmW devices, such as antennas or waveguides, are used. The optical components are much the same as in infrared or visible systems. However, there are differences in detail. As there are relatively few suitable lens materials, mirrors assume greater importance than in the visible region. As the most sensitive detectors at THz frequencies are cryogenically cooled in dedicated cryostats, windows are required, which hold the vacuum while allowing the THz radiation to enter with as little loss as possible. Due to the absorption of THz radiation by atmospheric water vapor, the optical path often needs to be evacuated and, therefore, windows are also needed for this. The subsidiary components of an optical system such as filters, polarizers are nowadays as well developed in the THz region as for the visible and infrared regions, and methods for providing such components with photonic bandgap structures or metamaterials are under way.